Kamal Mahtani's blog
Are you sitting comfortably?
For those interested in the history of medicine you may have heard of Jeremy Morris (1910-2009). Dr Morris was a Scottish epidemiologist who, during the 1950s, was involved in establishing the link between a lack of physical activity and increased cardiovascular risk. In his paper, published in The Lancet, Dr Morris and his colleagues teamed up with London Transport, The Post Office and The Treasury Medical Service. The London Transport Workers Study observed 31,000 men aged 35-64 employed as bus drivers and conductors. They found that you were more likely to suffer from coronary heart disease as a sedentary driver, than as a conductor who climbed the stairs of a double decker bus. This finding also reflected their data in postal workers who were less likely to suffer with coronary heart disease that desk based civil servants. Although a number of limitations of their work were acknowledged, it was clear that a link had been made and in 1996 these contributions were recognized when he was awarded the first International Olympic Committee Prize for Sport Sciences.
Over 60 years later the data linking physical inactivity with ill health continues. Last week researchers at The University of Leicester published a paper on the association between sedentary time in adults and the risk of diabetes, cardiovascular disease and death. They collected data from 18 individual studies. For each one they calculated the risk of ill health associated with the highest sedentary time versus the risk with the lowest, a relative risk (RR). They found a 112% increase in the relative risk of diabetes, a 147% increase in cardiovascular events and a 90% increase in the risk of cardiovascular mortality. With figures like that it’s no wonder the results made the widespread public media. Of the 18 included studies the authors used for their analysis, 13 used TV viewing as their sedentary measure, which was interesting as the authors also stated in their introduction that TV viewing may not be a good representation of total sedentary time, perhaps suggesting it could be an over- or under- estimate. The other 5 studies used self-reporting of sedentary time which is notorious for having poor reliability. That said if someone asked you how much time you sit down in a day, do you think you were more likely to over or under estimate? The other interesting point was that the risk seemed independent upon how much activity you were doing outside the sedentary time. So even if you go to the gym for 1 hour, it’s what you do with the other 23 hours that seem to count as well.
Despite some limitations, the paper adds to the work of Dr Morris and others, supporting the evidence linking physical inactivity and ill health.
Crikey!...even now you might be sitting down and reading this. I better add some handy tips for standing up while sitting.
As for me, I’ve been sitting down and writing this for 40 minutes, time for a stretch I think…
Why bringing home the bacon isn't always the best thing
We consume too much salt. The problem is that high salt levels are associated with increased blood pressure and therefore increased risk of heart disease and stroke. Although the government says we should be consuming no more than 6 grams per day, we probably consume about 9 grams per day. The majority of that salt comes from processed foods rather than from adding salt at the table. Now a new survey from the UK based "Consensus Action on Salt & Health" (CASH) reveals what most lovers of a bacon sandwich probably don’t want to hear. Bacon has superseded ready meals, as the second highest contributor to salt in our diet with, in some cases, just 2 rashers providing half the total recommended daily amount. The survey reviewed the salt content of over 120 bacon packs available from high street supermarkets and found wide variations in bacon salt levels within the same supermarket. For example the supermarket Morrisons sells a Savers Smoked Rindless Back Bacon product with 6.8g salt per 100g bacon while also selling a different own brand pack with 2g salt per 100g. The CASH website has posted an industry response from Morrisons reporting that the supermarket will be targeting lower salt bacon products in the New Year.
So if bacon is the second highest contributor to salt, what is the first? I’m afraid it’s the bread holding your bacon sandwich together. Pre-packed bread and rolls remains the number 1 contributor to salt in the UK diet. The rest of the list includes fat spreads, cheese, sausages, cereals, ham and morning goods.
Hmmm….I think I’ll stick to my porridge for breakfast from now on.
Is Christmas bad for you?
Ah, the festive season. One of my favourite times of year: all the family around, food, a bit of time off work, food, the presents, food, The Queen’s speech, food etc. A wave of emotion floods all my senses at the mere thought.
But can Christmas be bad for your health?
First guilty thoughts go to the waist line. So how much weight do we put on during the festive period? In answering that question I came across an observational study in the British Medical Journal from 1985. In it 22 healthy adults and 13 Type 2 diabetics were weighed one month before and one month after Christmas. All participants had an increase in weight which was on average 1.7lbs (0.8kg). The authors suggested that this came from an additional 6000 kcal they ingested over that period. They also found a slight but significant increase in fasting triglyceride and cholesterol concentrations. Although they reassuringly conclude that the results from their study were unlikely to affect any future Christmas.
Slightly more recently, a prospective cohort study published in the New England Journal of Medicine in 2000 suggested we probably don’t put on as much weight as we think we do over the festive period. In the study 195 adult volunteers were weighed at intervals before and after the holiday season, which included the Thanksgiving weekend. The volunteers gained an average of 0.8lb (0.4kg) during the six weeks between Thanksgiving and New Year's Day, which was far less than what they thought they had put on, which was nearer 5lbs (2.3kg).
So perhaps things aren’t so bad then? Not quite. It’s also about what we eat. There is now little doubt of the role that high salt consumption has in raising blood pressure and therefore increasing the chances of having a heart attack or stroke. The Government had set a target to reduce the salt intake of the population to 6g per person per day by 2010. In reality we probably consume more like 9g per day. Apparently it’s worse at Christmas! A survey this month from the Consensus Action on Salt&Health (CASH) found that an average Christmas day of pre-lunch snacks, canapés and a three course Christmas dinner could contain as much as 15.7g of salt. Admittedly the main culprits are processed foods. The survey makes reference to the fact that a significant proportion of salt consumed could be reduced by simply preparing your own vegetables and avoiding adding salt during the cooking. Likewise choosing the low salt equivalents, such as with crisps, may halve your salt consumption. Or how about a Yorkshire Wensleydale with apricot instead of a Creamy Blue Stilton this year? Again half the salt level.
So am I suffering from “Bah! Humbug syndrome”? Far from it! I fully intend to enjoy the holiday season with all of the above. I’ll just keep one eye on how tight my belt feels and perhaps think a little before that second portion.